Method and apparatus for changing discontinuous reception cycle in wireless communication system

ABSTRACT

A method and apparatus for changing a Discontinuous Reception (DRX) cycle in a wireless communication system is provided. A wireless device configures a short DRX cycle and a long DRX cycle. When the wireless device receives a PDCCH indicating a new data transmission, it determines that the short DRX cycle is used and a running drxShortCycleTimer is stopped for the DRX operation. Discontinuous reception (DRX) cycle can be configured flexibly according to the new data transmission and a CSI report between the UE and the eNB can be complied with accurately and frequently.

TECHNICAL FIELD

The present invention relates to wireless communications, and moreparticularly, to a method and apparatus for changing a DRX cycle in awireless communication system.

BACKGROUND ART

3rd generation partnership project (3GPP) long term evolution (LTE) isan improved version of a universal mobile telecommunication system(UMTS) and a 3GPP release 8. The 3GPP LTE uses orthogonal frequencydivision multiple access (OFDMA) in a downlink, and uses singlecarrier-frequency division multiple access (SC-FDMA) in an uplink. The3GPP LTE employs multiple input multiple output (MIMO) having up to fourantennas. In recent years, there is an ongoing discussion on 3GPPLTE-advanced (LTE-A) that is an evolution of the 3GPP LTE.

Discontinuous reception (DRX) is a method for reducing batteryconsumption by allowing a user equipment (UE) to discontinuously monitora downlink channel. When the DRX is configured, the UE discontinuouslymonitors the downlink channel. Otherwise, the UE continuously monitorsthe downlink channel.

Recently, many applications require an always-on characteristic.Always-on is a characteristic in which the UE is always connected to anetwork so as to directly transmit data whenever necessary.

However, since battery consumption is great when the UE continuouslymaintains the network connection, a proper DRX is configured in acorresponding application to guarantee the always-on characteristicwhile reducing battery consumption.

Recently, several various applications are running in parallel in oneUE, and thus it is not easy to configure one DRX suitable for all of theapplications. This is because, even if an optimal DRX is configured fora specific application, it may be a not proper DRX configuration withrespect to other applications which are running in parallel.

There is a need for a method for operating the DRX in a more flexiblemanner.

DISCLOSURE Technical Problem

The present invention provides a method and apparatus for changing a DRXcycle in a wireless communication system.

The present invention also provides a method and apparatus for changinga DRX cycle in consideration of a new data transmission in a wirelesscommunication system.

The present invention also provides a method and apparatus forcontrolling to not use a long DRX cycle with restriction on DRXoperation in a wireless communication system.

Technical Solution

In an aspect, a method for changing a DRX (Discontinuous Reception)cycle in a wireless communication system is provided. The methodincludes configuring a short DRX cycle and a long DRX cycle; receiving aphysical downlink control channel (PDCCH) indicating a new datatransmission; and using the short DRX cycle if the received PDCCHindicates the new data transmission.

The method may further include stopping a drxShortCycleTimer if thedrxShortCycleTimer is running.

The method may further include using the long DRX cycle if the receivedPDCCH does not indicate the new data transmission..

In another aspect, a wireless device for changing DRX (DiscontinuousReception) cycle in a wireless communication system is provided. Thewireless device includes a radio frequency unit for receiving a radiosignal; and a processor, operatively coupled with the radio frequencyunit, configured to configure a short DRX cycle and a long DRX cycle,receive a physical downlink control channel (PDCCH) indicating a newdata transmission, and use the short DRX cycle if the received PDCCHindicates the new data transmission.

Advantageous Effects

Discontinuous reception (DRX) cycle can be configured flexibly and achanging a DRX cycle in consideration of a new data transmission betweenthe UE and the eNB can be complied with accurately. More details, the UEmay not use a long DRX cycle when the new data transmission is expected.It can be advantaged that a CSI reporting can performed in considerationof data traffic when a DRX operation is configured for the UE.

DESCRIPTION OF DRAWINGS

FIG. 1 shows a wireless communication system to which the presentinvention is applied.

FIG. 2 is a diagram showing a radio protocol architecture for a userplane to which the present invention is applied.

FIG. 3 is a diagram showing a radio protocol architecture for a controlplane to which the present invention is applied to which the presentinvention is applied

FIG. 4 shows a DRX cycle to which the present invention is applied.

FIG. 5 shows active time for DRX operation to which the presentinvention is applied.

FIG. 6 shows an example of a transition of a DRX cycle to which thepresent invention is applied.

FIG. 7 shows an example of DRX operation with a Long DRX cycle which thewireless communication system is applied.

FIG. 8 shows an example of DRX operation with a short DRX cycleaccording to an exemplary embodiment of the present invention.

FIG. 9 shows a flowchart for changing a DRX cycle according to anexemplary embodiment of the present invention.

FIG. 10 shows a block diagram showing a wireless communication systemaccording to an exemplary embodiment of the present invention.

MODE FOR INVENTION

FIG. 1 shows a wireless communication system to which the presentinvention is applied. The wireless communication system may also bereferred to as an evolved-UMTS terrestrial radio access network(E-UTRAN) or a long term evolution (LTE)/LTE-A system.

The E-UTRAN includes at least one base station (BS) 20 which provides acontrol plane and a user plane to a user equipment (UE) 10. The UE 10may be fixed or mobile, and may be referred to as another terminology,such as a mobile station (MS), a user terminal (UT), a subscriberstation (SS), a mobile terminal (MT), a wireless device, etc. The BS 20is generally a fixed station that communicates with the UE 10 and may bereferred to as another terminology, such as an evolved node-B (eNB), abase transceiver system (BTS), an access point, etc.

The BSs 20 are interconnected by means of an X2 interface. The BSs 20are also connected by means of an Si interface to an evolved packet core(EPC) 30, more specifically, to a mobility management entity (MME)through S1-MME and to a serving gateway (S-GW) through S1-U.

The EPC 30 includes an MME, an S-GW, and a packet data network-gateway(P-GW). The MME has access information of the UE or capabilityinformation of the UE, and such information is generally used formobility management of the UE. The S-GW is a gateway having an E-UTRANas an end point. The P-GW is a gateway having a PDN as an end point.

Layers of a radio interface protocol between the UE and the network canbe classified into a first layer (L1), a second layer (L2), and a thirdlayer (L3) based on the lower three layers of the open systeminterconnection (OSI) model that is well-known in the communicationsystem. Among them, a physical (PHY) layer belonging to the first layerprovides an information transfer service by using a physical channel,and a radio resource control (RRC) layer belonging to the third layerserves to control a radio resource between the UE and the network. Forthis, the RRC layer exchanges an RRC message between the UE and the BS.

FIG. 2 is a diagram showing a radio protocol architecture for a userplane. FIG. 3 is a diagram showing a radio protocol architecture for acontrol plane. The user plane is a protocol stack for user datatransmission. The control plane is a protocol stack for control signaltransmission.

Referring to FIGS. 2 and 3, a PHY layer provides an upper layer with aninformation transfer service through a physical channel. The PHY layeris connected to a medium access control (MAC) layer which is an upperlayer of the PHY layer through a transport channel. Data is transferredbetween the MAC layer and the PHY layer through the transport channel.The transport channel is classified according to how and with whatcharacteristics data is transferred through a radio interface.

Between different PHY layers, i.e., a PHY layer of a transmitter and aPHY layer of a receiver, data is transferred through the physicalchannel. The physical channel may be modulated using an orthogonalfrequency division multiplexing (OFDM) scheme, and may utilize time andfrequency as a radio resource.

Functions of the MAC layer include mapping between a logical channel anda transport channel and multiplexing/de-multiplexing on a transportblock provided to a physical channel over a transport channel of a MACservice data unit (SDU) belonging to the logical channel. The MAC layerprovides a service to a radio link control (RLC) layer through thelogical channel.

Functions of the RLC layer include RLC SDU concatenation, segmentation,and reassembly. To ensure a variety of quality of service (QoS) requiredby a radio bearer (RB), the RLC layer provides three operation modes,i.e., a transparent mode (TM), an unacknowledged mode (UM), and anacknowledged mode (AM). The AM RLC provides error correction by using anautomatic repeat request (ARQ).

Functions of a packet data convergence protocol (PDCP) layer in the userplane include user data delivery, header compression, and ciphering.Functions of a PDCP layer in the control plane include control-planedata delivery and ciphering/integrity protection.

A radio resource control (RRC) layer is defined only in the controlplane. The RRC layer serves to control the logical channel, thetransport channel, and the physical channel in association withconfiguration, reconfiguration and release of radio bearers (RBs). An RBis a logical path provided by the first layer (i.e., the PHY layer) andthe second layer (i.e., the MAC layer, the RLC layer, and the PDCPlayer) for data delivery between the UE and the network.

The setup of the RB implies a process for specifying a radio protocollayer and channel properties to provide a particular service and fordetermining respective detailed parameters and operations. The RB can beclassified into two types, i.e., a signaling RB (SRB) and a data RB(DRB). The SRB is used as a path for transmitting an RRC message in thecontrol plane. The DRB is used as a path for transmitting user data inthe user plane.

When an RRC connection is established between an RRC layer of the UE andan RRC layer of the network, the UE is in an RRC connected state (alsomay be referred to as an RRC connected mode), and otherwise the UE is inan RRC idle state (also may be referred to as an RRC idle mode).

Data is transmitted from the network to the UE through a downlinktransport channel. Examples of the downlink transport channel include abroadcast channel (BCH) for transmitting system information and adownlink-shared channel (SCH) for transmitting user traffic or controlmessages. The user traffic of downlink multicast or broadcast servicesor the control messages can be transmitted on the downlink-SCH or anadditional downlink multicast channel (MCH). Data is transmitted fromthe UE to the network through an uplink transport channel. Examples ofthe uplink transport channel include a random access channel (RACH) fortransmitting an initial control message and an uplink SCH fortransmitting user traffic or control messages.

Examples of logical channels belonging to a higher channel of thetransport channel and mapped onto the transport channels include abroadcast channel (BCCH), a paging control channel (PCCH), a commoncontrol channel (CCCH), a multicast control channel (MCCH), a multicasttraffic channel (MTCH), etc.

The physical channel includes several OFDM symbols in a time domain andseveral subcarriers in a frequency domain. One subframe includes aplurality of OFDM symbols in the time domain. A resource block is aresource allocation unit, and includes a plurality of OFDM symbols and aplurality of subcarriers. Further, each subframe may use particularsubcarriers of particular OFDM symbols (e.g., a first OFDM symbol) of acorresponding subframe for a physical downlink control channel (PDCCH),i.e., an L1/L2 control channel. A transmission time interval (TTI) is aunit time of subframe transmission.

The 3GPP LTE classifies a physical channel into a data channel, i.e., aphysical downlink shared channel (PDSCH) and a physical uplink sharedchannel (PUSCH), and a control channel, i.e., a physical downlinkcontrol channel (PDCCH), a physical control format indicator channel(PCFICH) and a physical hybrid-ARQ indicator channel (PHICH), and aphysical uplink control channel (PUCCH).

The PCFICH transmitted in a 1st OFDM symbol of the subframe carries acontrol format indicator (CFI) regarding the number of OFDM symbols(i.e., a size of the control region) used for transmission of controlchannels in the subframe. The UE first receives the CFI on the PCFICH,and thereafter monitors the PDCCH.

The PDCCH is a downlink control channel, and is also called a schedulingchannel in a sense that it carries scheduling information. Controlinformation transmitted through the PDCCH is referred to as downlinkcontrol information (DCI). The DCI may include resource allocation ofthe PDSCH (this is referred to as a downlink (DL) grant), resourceallocation of a PUSCH (this is referred to as an uplink (UL) grant), aset of transmit power control commands for individual UEs in any UEgroup and/or activation of a voice over Internet protocol (VoIP).

The wireless communication system as 3GPP LTE of the present inventionuses blind decoding for PDCCH detection. The blind decoding is a schemein which a desired identifier is de-masked from a CRC of a PDCCH(referred to as a candidate PDCCH) to determine whether the PDCCH is itsown channel by performing CRC error checking.

A BS determines a PDCCH format according to DCI to be transmitted to aUE. Thereafter, the BS attaches a cyclic redundancy check (CRC) to theDCI, and masks a unique identifier (referred to as a radio networktemporary identifier (RNTI)) to the CRC according to an owner or usageof the PDCCH.

Now, discontinuous reception (DRX) in a wireless communication system,as example, 3GPP LTE will be described.

The DRX is a method for reducing battery consumption of a UE by allowingthe UE to discontinuously monitor a downlink channel.

FIG. 4 shows a DRX cycle to which the present invention is applied.

A DRX cycle specifies the periodic repetition of the on-durationfollowed by a possible period of inactivity. The DRX cyclic includes anon-duration and an off-duration. The on-duration is a duration in whicha UE monitors a PDCCH within the DRX cycle. The DRX cycle has two types,i.e., a long DRX cycle and a short DRX cycle. The long DRX cycle whichhas a long period can minimize battery consumption of the UE. The shortDRX cyclic which has a short period can minimize a data transmissiondelay.

When the DRX is configured, the UE may monitor the PDCCH only in theon-duration and may not monitor the PDCCH in the off-duration.

An onDuration timer is used to define the on-duration. The on-durationcan be defined as a duration in which the onDuration timer is running.The onDuration timer may specify the number of consecutivePDCCH-subframe(s) at the beginning of a DRX Cycle. The PDCCH-subframespecifies a subframe in which the PDCCH is monitored.

In addition to the DRX cycle, a duration in which the PDCCH is monitoredcan be further defined. A duration in which the PDCCH is monitored iscollectively referred to as an active time.

A drx-Inactivity timer deactivates the DRX. If the drx-Inactivity timeris running, the UE continuously monitors the PDCCH irrespective of theDRX cycle. The drx-Inactivity timer starts upon receiving an initial ULgrant or DL grant on the PDCCH. The drx-Inactivity timer may specify thenumber of consecutive PDCCH-subframe(s) after successfully decoding aPDCCH indicating an initial UL or DL user data transmission for this UE.

A HARQ RTT timer defines a minimum duration in which the UE expects HARQretransmission. The HARQ RTT timer may specify the minimum amount ofsubframe(s) before a DL HARQ retransmission is expected by the UE.

A drx-Retransmission timer defines a duration in which the UE monitorsthe PDCCH while expecting DL retransmission. The drx-Retransmissiontimer may specify the maximum number of consecutive PDCCH-subframe(s)for as soon as a DL retransmission is expected by the UE. After initialDL transmission, the UE starts the HARQ RTT timer. When an error isdetected for the initial DL transmission, the UE transmits NACK to a BS,stops the HARQ RTT timer, and runs the drx-Retransmission timer. The UEmonitors the PDCCH for DL retransmission from the BS while thedrx-Retransmission timer is running.

An Active Time can include an on-duration in which the PDCCH isperiodically monitored and a duration in which the PDCCH is monitoreddue to an event occurrence.

When a DRX cycle is configured, the Active Time includes the time while:

-   -   onDuration timer or drx-Inactivity timer or drx-Retransmission        timer or mac-ContentionResolution timer is running; or    -   a Scheduling Request is sent on PUCCH and is pending; or    -   an uplink grant for a pending HARQ retransmission can occur and        there is data in the corresponding HARQ buffer; or    -   a PDCCH indicating a new transmission addressed to the C-RNTI of        the UE has not been received after successful reception of a        Random Access Response for the preamble not selected by the UE.

FIG. 5 shows active time for DRX operation to which the presentinvention is applied.

When DRX is configured, the UE shall for each subframe:

-   -   if a HARQ RTT Timer expires in this subframe and the data of the        corresponding HARQ process was not successfully decoded:    -   start the drx-Retransmission timer for the corresponding HARQ        process.    -   if a DRX Command MAC CE (control element) is received:    -   stop onDuration timer and drx-Inactivity timer.    -   if drx-InactivityTimer expires or a DRX Command MAC CE is        received in this subframe:    -   if the Short DRX cycle is configured:        -   start or restart drx-ShortCycle timer and use the Short DRX            Cycle.    -   else:        -   use the Long DRX cycle.    -   if drx-ShortCycle timer expires in this subframe:    -   use the Long DRX cycle.    -   If the Short DRX Cycle is used and [(SFN*10)+subframe number]        modulo (shortDRX-Cycle)=(drxStartOffset) modulo        (shortDRX-Cycle); or    -   if the Long DRX Cycle is used and [(SFN*10)+subframe number]        modulo (longDRX-Cycle)=drxStartOffset:        -   start onDuration timer.    -   during the Active Time, for a PDCCH-subframe, if the subframe is        not required for uplink transmission for half-duplex FDD UE        operation and if the subframe is not part of a configured        measurement gap:    -   monitor the PDCCH;    -   if the PDCCH indicates a DL transmission or if a DL assignment        has been configured for this subframe:        -   start the HARQ RTT timer for the corresponding HARQ process;        -   stop the drx-Retransmission timer for the corresponding HARQ            process.    -   if the PDCCH indicates a new transmission (DL or UL):        -   start or restart drx-Inactivity timer.    -   when not in Active Time, type-0-triggered SRS shall not be        reported.    -   if CQI masking (cqi-Mask) is setup by upper layers:    -   when onDurationTimer is not running, CQI/PMI/RI/PTI on PUCCH        shall not be reported.    -   else:    -   when not in Active Time, CQI/PMI/RI/PTI on PUCCH shall not be        reported.

As mentioned, the active-time is defined a total duration that the UE isawake. This includes the on-duration of the DRX cycle, the time UE isperforming continuous reception while the inactivity timer has notexpired and the time UE is performing continuous reception while waitingfor a DL retransmission after one HARQ RTT. Based on the above theminimum active time is of length equal to on-duration, and the maximumis undefined (infinite).

FIG. 6 shows an example of a transition of a DRX cycle to which thepresent invention is applied.

Upon receiving initial transmission from an eNB, a drx-Inactivity timer(also referred to as a first timer or an inactivity timer) starts (stepS610). A UE continuously monitors a PDCCH while the drx-Inactivity timeris running.

If the drx-Inactivity timer expires or if a DRX command is received fromthe eNB, the UE transitions to a short DRX cycle (step S620). Then, thedrx-ShortCycle timer (also referred to as a second timer or a DRX cycletimer) starts.

The DRX command can be transmitted as a MAC CE, and can be called a DRXindicator that indicates a transition to the DRX. The DRX command MAC CEis identified through a long channel ID (LCID) of a MAC PDU subheader.

While the drx-ShortCycle timer is running, the UE operates in the shortDRX cycle. If the drx-ShortCycle timer expires, the UE transitions to along DRX cycle.

If the short DRX cyclic is pre-set, the UE transitions to the short DRXcycle. If the short DRX cyclic is not pre-set, the UE can transition tothe long DRX cycle.

A value of HARQ RTT timer is fixed to 8 ms (or 8 subframes). Other timervalues (i.e., an onDuration timer, a drx-Inactivity timer, adrx-Retransmission timer, a mac-ContentionResolution timer, etc.) can bedetermined by the eNB through an RRC message. The eNB can configure thelong DRX cycle and the short DRX cycle through the RRC message.

FIG. 7 shows a situation of DRX operation to which a wirelesscommunication system is applied, i.e., the situation where the UE usesthe long DRX cycle while receiving at least one PDCCH includinginformation on radio resource allocation from the BS.

Referring to FIG.7, the UE with DRX operation can be configured totransmit CSI report and periodical SRS to the BS according to a CSIconfiguration of the BS.

This means that the UE is configured to preform CSI and SRS transmissiononly at the subframe corresponding to the On Duration of the DRX cycleaccording to the DRX and CSI configuration of the BS. At this step, theBS transmits a RRC signal to set the UE to the configuration for a DRXoperation and the configuration for CSI/SRS transmission. Also, the CSItransmission and SRS transmission are set by the BS, which are limitedto the operation of the UE related to the CSI transmission with CQImasking (cqi-Mask) scheme and periodic SRS transmission. The CSItransmission includes a transmission of CQI/PMI/RI/PTI on a PUCCH, whichis the configuration sets to transmit at On Duration of the DRX cycle.Also, the UE provides a uplink state by periodically sending a SoundingReference Signal (SRS), and this periodic SRS transmission is called atype-0-triggered SRS. The SRS transmission according to the presentinvention includes the limitation to type-0-triggered SRS.

When the UE is configured to use both Short DRX Cycle (700) and Long DRXcycle(760) for the DRX operation, the UE starts a drx-shortCycletimer(720) when a drx-Inactivity timer expires(730), and the UE startsusing the Long DRX cycle(760) if the drx-ShortCycle timer expires(720).

When the drx-ShortCycle timer is running, the UE will continuouslyresume the drx-Inactivity timer if the UE which uses the Short DRX cyclecontinuously receives at least one PDCCH including information on newradio resource allocation from the BS at the subframe in which thedrx-Inactivity timer is running. However, since the drx-Inactivity timerdoes not expire because of the receiving at least one PDCCHcontinuously, the running the drx-ShortCycle timer expires afterpredetermined time, and the UE finally transits from a Short DRX cycleto the long DRX cycle.

As a result, the UE transits the short DRX cycle to Long DRX cycle anduses the Long DRX cycle although it has to perform datatransmission/reception by receiving radio resource allocationinformation continuously from the BS, it is caused the problem of notbeing able to perform the CSI transmission with sufficient frequencyeven if the UE is configured to transmit the CSI and SRS reports at thesubframe corresponding to On Duration.

In addition, this problem causes difficulties with allocating radioresources correctly for the UE and making a low system performance inview of the BS. Therefore, this operation of the DRX is not proper andthe DRX operation needs to be modified.

In consideration of this problem and in order to perform the CSI reportand the SRS transmission with sufficient and correct frequency, thepresent invention is disclosed a solution for controlling to not use theLong DRX cycle by stopping the running the drx-ShortCycle timer when newdata transmissions on at least one PDCCH are expected. In other words,the present invention discloses a controlling scheme about a change ofDRX cycle by stopping the drxShortCycle timer.FIG. 8 shows an example ofchange DRX cycle according to an exemplary embodiment of the presentinvention. For example, the present invention includes a use of the LongDRX cycle is prohibited especially when a PDCCH indicating transmissionof new data is received from the BS.

Referring to FIG. 8, the UE is configured to use both the Short DRXCycle and the long DRX cycle. If the UE which uses the Short DRX cyclecontinuously receives at least one PDCCH including information on a newradio resource allocation from the BS, herein the PDCCH includes a newdata transmission, at the subframe in which a drx-Inactivity timer isrunning while the drx-ShortCycle timer is running, the UE continuouslyresumes the drx-Inactivity timer, and the UE starts to use the Short DRXcycle (800).

If the drxShortCycle timer is running at this step, the UE controls thatthe running drxShortCycle timer is stopped (825).

In other words, in the present invention, if the UE using the Short DRXcycle determines to continuously perform the new data transmission withthe BS, the UE determines to use the Short DRX cycle by not applying theLong DRX cycle with restriction. The DRX cycle change is restricted bystopping of the drxShortCycle timer, in order to bar the conventionalDRX operation of changing the Long DRX cycle when the drxShortCycletimer expired.

In relation to this situation, the operation of changing a DRX cyclewill be described with reference to FIG. 9.

FIG. 9 shows an example on the operation process of the UE according tothe present invention, in which the DRX cycle is changed inconsideration of the stop of drxShortCycle timer when the UE operates tobe expected to receive the new data transmission.

Referring to FIG. 9, the UE sets configurations related to a DRXconfiguration and a CSI reporting transmission. At this step, the UE canbe configured to use the Short DRX cycle and the long DRX cycle with theDRX configuration (910). In order to set these configurations related tothe DRX configuration and CSI transmission, the UE can receive a RRCsignaling from the BS. In other words, the BS transmits the RRC signalto the UE in order to configure to use two types of DRX cycles such asthe Short DRX cycle and the Long DRX cycle.

At this step, the UE can receive information on radio resourceallocation from the BS through the PDCCH during the On Durationpredetermined according to the DRX configuration (920). Herein the PDCCHincludes a new data transmission. At this step, the UE receives, fromthe base station, the PDCCH indicating a new data transmission (920).The reception of the PDCCH includes monitoring of the PDCCH at OnDuration predetermined with the Short DRX cycle. The UE determineswhether the new data transmission is existed or not by checking a NewData Indicator (NDI) in the received PDCCH.

For example, if initial transmission(new data transmission) is set, theUE can receive a PDCCH including the NDI with 0 of value(bit) forindicating the initial transmission(or new data transmission), so the UEdetermines the data transmission is new or retransmitted by the NDIvalue(bit). Herein the data transmission includes uplink from the UE toBS, and downlink from the BS to the UE. This invention includes the NDIis applied for the uplink data transmission or the downlink datatransmission.

Then, the UE starts or resumes the drx-Inactivity timer is operated witha predetermined length of subframe by receiving the PDCCH. At the sametime, the UE starts to use the Short DRX cycle, and stops the runningthe drxShortCycle timer if the drxShortCycle timer is running (930).That is the UE controls to not use the Long DRX cycle when the UEdetermines that the PDCCH including the new data transmission isreceived. Therefore, the UE can bar a transition to the Long DRX cyclewhen the PDCCH indicating NDI is existed from the BS.

The present invention, as described above, provides the advantages ofusing the Short DRX cycle by not using the change to the Long DRX cyclewhen the UE performing DRX operation continuously performs datatransmission with the BS. It is the advantage of performing CSItransmission and SRS transmission at the subframe corresponding topredetermined On Duration with sufficient frequency by performing DRXoperation according to Short DRX cycle. Therefore, the present inventionallows the BS to correctly acquire the information for performing radioresource allocation, thereby enhancing the performance of the entiresystem.

Although the aforementioned embodiment shows the DRX operation of the UEfor example, the proposed invention is applicable to a DRX operation ofa machine to machine (M2M) device or a machine-type communication (MTC)device. MTC is one type of data communication including one or moreentities not requiring human interactions. That is, the MTC refers tothe concept of communication performed by a machine device, not aterminal used by a human user, by using the existing wirelesscommunication network. The machine device used in the MTC can be calledan MTC device. There are various MTC devices such as a vending machine,a machine of measuring a water level at a dam, etc.

FIG. 10 is a block diagram showing a wireless communication systemaccording to an embodiment of the present invention.

A BS 1050 includes a processor 1051, a memory 1052, and a radiofrequency (RF) unit 1053. The memory 1052 is coupled to the processor1051, and stores a variety of information for driving the processor1051. The RF unit 1053 is coupled to the processor 51, and transmitsand/or receives a radio signal. The processor 1051 implements theproposed functions, procedures, and/or methods. In the embodiments ofFIG. 8 to FIG. 10, the operation of the BS can be implemented by theprocessor 51.

Especially, the processor 1051 configures and sets the DRX configurationand CSI transmission configuration with CQI masking on the UE. Herein,the DRX configuration is included to set to UE with both the Short DRXcycle and the Long DRX cycle. This processor 1051 controls CSItransmission configuration to UE in order to correctly perform CSIreport at specific subframe during On Duration configured for the CSItransmission configuration with CQI masking under the environment ofperforming the DRX operation,

The processor 1051 also estimates that the UE performs the DRX cycleusing with the Short cycle not to use of the Long DRX cycle by stoppingthe drx-ShortCycle timer of the UE while the new transmission/receptionis occurred, so that the processor 1051 also estimates the CSI report atthe specific subframe On Duration with the DRX cycle estimated inconsideration of the data transmission of the initial transmission orretransmission. In addition to, the processor 1051 configures the PDCCHwith NDI set to indicate the initial data transmission. Therefore, moreproper and clear DRX operation is suggested in consideration of the datatransmission between the UE and BS,

A wireless device 1060 includes a processor 1061, a memory 1062, and anRF unit 1063. The memory 1062 is coupled to the processor 1061, andstores a variety of information for driving the processor 1061. The RFunit 1063 is coupled to the processor 1061, and transmits and/orreceives a radio signal. The processor 1061 implements the proposedfunctions, procedures, and/or methods. In the embodiments of the FIG. 8to FIG. 10, the operation of the UE can be implemented by the processor1061.

Especially, the processor 1061 configures the DRX configuration and theCSI transmission configuration by checking a RRC signaling received bythe RF unit 1063. Herein, the DRX configuration is included the statewhere both the Short DRX cycle and the Long DRX cycle are configured.This processor 1061, in order to correctly perform CSI report at OnDuration configured for transmission under the environment of performingthe DRX operation, i.e., configured with CQI masking, can selectivelycontrol transition of DRX cycle in consideration that the drx-Inactivitytimer is running or not if the drx-ShortCycle timer which has beenrunning by using the Short DRX cycle expires.

The processor 1051 controls to use the Short DRX cycle, not to use theLong DRX cycle by checking that the PDCCH indicating the new datatransmission from the BS is received, and the PDCCH is checked toindicate the new data transmission. The processor 1061 checks the NDI inthe PDCCH is set to indicate 0 of value(bit) for indicating the initialtransmission(or new data transmission).

The processor 1061 controls a change of the DRX cycle selectively formore clear DRX operation by stopping of the drx-ShortCycle timer inorder to not to use the Long DRX cycle when the drx-ShortCycle timerexpires, and checking the NDI in the PDCCH. Meanwhile, the processor1061 determines to keep the use the Short DRX cycle if radio resourceallocation information for the new data transmission via at least onePDCCH from the BS is received, and restriction of the use to the LongDRX cycle is made.

The processor 1061 also determines to CSI report at the specificsubframe On Duration determined according to the maintained DRX cycle.Therefore, the processor 1061 controls to perform CSI transmission atthe On Duration interval determined with the Short DRX cycle in order toprovide channel state reports to the BS to when it is need to receiveradio resource allocation information for the new datatransmission/reception with effect.

Therefore, more clear and correct DRX operation in consideration of thenew data traffic is provided, in addition to more frequent CSI reportsto be allocated radio resource allocation information with more proper.

The technical concept of the present invention is based on provisionaldocuments as described in the below.

<Start of Priority Document>

In this invention, to send sufficiently frequent CQI/PMI/PTI/RI reportsduring the drx-Inactivity timer is running, the UE forbids the DRX Cycletransition from the Short DRX Cycle to the Long DRX Cycle when there ison-going data transmission.

Invention 3.1: Selective DRX Cycle change.

The eNB configures to the UE,

-   -   the DRX functionality including the Short DRX cycle and the Long        DRX Cycle,    -   CQI reports including CQI masking

When the UE is configured with the DRX functionality,

-   -   The UE uses the short DRX cycle;    -   The UE starts drx-ShortCycle timer.    -   The UE uses the long DRX cycle at the expiry of drx-ShortCycle        timer.

If the UE receives the PDCCH indicating a new transmission in UL or DL,

-   -   The UE starts or restarts drx-Inactivity timer.    -   When drx-ShortCycle timer expires,        -   The UE checks if drx-Inactivity timer is running            -   If drx-Inactivity timer is running, the UE uses the                Short DRX Cycle            -   Else, the UE uses the Long DRX Cycle.    -   The UE applies the CQI masking configuration.        -   The UE applies the CQI masking and reports CQI/PMI/RI/PTI on            PUCCH when onDurationTimer is running.    -   When the drx-Inactivity timer expires,        -   The UE starts drx-ShortCycle timer.        -   The UE uses Short DRX Cycle.        -   Then, when drx-ShortCycle timer expires, the UE uses the            Long DRX Cycle.

Invention 3.2: The UE stops drx-ShortCycle timer.

The eNB configures to the UE,

-   -   the DRX functionality including the Short DRX cycle and the Long        DRX Cycle,    -   CQI reports including CQI masking

When the UE is configured with the DRX functionality,

-   -   The UE uses the short DRX cycle;    -   The UE starts drx-ShortCycle timer.    -   The UE uses the long DRX cycle at the expiry of drx-ShortCycle        timer.

If the UE receives the PDCCH indicating a new transmission in UL or DL,

-   -   The UE starts or restarts drx-Inactivity timer.    -   The UE uses the Short DRX Cycle.        -   The UE stops drx-ShortCycle timer, if running;    -   The UE applies the CQI masking configuration.        -   The UE applies the CQI masking and reports CQI/PMI/RI/PTI on            PUCCH when onDurationTimer is running.    -   When the drx-Inactivity timer expires,        -   The UE uses Short DRX Cycle.        -   The UE starts drx-ShortCycle timer.        -   Then, when drx-ShortCycle timer expires, the UE uses the            Long DRX Cycle.

Text Proposal: TS36.321

For invention 1:

When DRX is configured, the UE shall for each subframe:

-   -   if a HARQ RTT Timer expires in this subframe and the data of the        corresponding HARQ process was not successfully decoded:    -   start the drx-RetransmissionTimer for the corresponding HARQ        process.    -   if a DRX Command MAC control element is received:    -   stop onDurationTimer;    -   stop drx-Inactivity timer.    -   if drx-Inactivity timer expires or a DRX Command MAC control        element is received in this subframe:    -   if the Short DRX cycle is configured:        -   start or restart drx-ShortCycle timer ;        -   use the Short DRX Cycle.    -   else:        -   use the Long DRX cycle.    -   if drx-ShortCycle timer expires in this subframe and if the        drx-Inactivity timer is not running:    -   use the Long DRX cycle.    -   If the Short DRX Cycle is used and [(SFN*10)+subframe number]        modulo (shortDRX-Cycle)=(drxStartOffset) modulo        (shortDRX-Cycle); or    -   if the Long DRX Cycle is used and [(SFN*10)+subframe number]        modulo (longDRX-Cycle)=drxStartOffset:    -   start onDurationTimer.    -   during the Active Time, for a PDCCH-subframe, if the subframe is        not required for uplink transmission for half-duplex FDD UE        operation and if the subframe is not part of a configured        measurement gap:    -   monitor the PDCCH;    -   if the PDCCH indicates a DL transmission or if a DL assignment        has been configured for this subframe:    -   start the HARQ RTT Timer for the corresponding HARQ process;    -   stop the drx-RetransmissionTimer for the corresponding HARQ        process.    -   if the PDCCH indicates a new transmission (DL or UL):    -   start or restart drx-Inactivity timer.    -   when not in Active Time, type-0-triggered SRS [2] shall not be        reported.    -   if CQI masking (cqi-Mask) is setup by upper layers:    -   when onDurationTimer is not running, CQI/PMI/RI/PTI on PUCCH        shall not be reported.    -   else:    -   when not in Active Time, CQI/PMI/RI/PTI on PUCCH shall not be        reported.

For invention 2:

When DRX is configured, the UE shall for each subframe:

-   -   if a HARQ RTT Timer expires in this subframe and the data of the        corresponding HARQ process was not successfully decoded:    -   start the drx-RetransmissionTimer for the corresponding HARQ        process.    -   if a DRX Command MAC control element is received:    -   stop onDurationTimer;    -   stop drx-Inactivity timer.    -   if drx-Inactivity timer expires or a DRX Command MAC control        element is received in this subframe:    -   if the Short DRX cycle is configured:        -   start or restart drx-ShortCycle timer;        -   use the Short DRX Cycle.    -   else:        -   use the Long DRX cycle.    -   if drx-ShortCycle timer expires in this subframe:    -   use the Long DRX cycle.    -   If the Short DRX Cycle is used and [(SFN*10)+subframe number]        modulo (shortDRX-Cycle)=(drxStartOffset) modulo        (shortDRX-Cycle); or    -   if the Long DRX Cycle is used and [(SFN*10)+subframe number]        modulo (longDRX-Cycle)=drxStartOffset:    -   start onDurationTimer.    -   during the Active Time, for a PDCCH-subframe, if the subframe is        not required for uplink transmission for half-duplex FDD UE        operation and if the subframe is not part of a configured        measurement gap:    -   monitor the PDCCH;    -   if the PDCCH indicates a DL transmission or if a DL assignment        has been configured for this subframe:    -   start the HARQ RTT Timer for the corresponding HARQ process;    -   stop the drx-RetransmissionTimer for the corresponding HARQ        process.    -   if the PDCCH indicates a new transmission (DL or UL):    -   start or restart drx-Inactivity timer.    -   use the Short DRX Cycle.    -   stop drx-ShortCycle timer.    -   when not in Active Time, type-0-triggered SRS [2] shall not be        reported.    -   if CQI masking (cqi-Mask) is setup by upper layers:    -   when onDurationTimer is not running, CQI/PMI/RI/PTI on PUCCH        shall not be reported.    -   else:    -   when not in Active Time, CQI/PMI/RI/PTI on PUCCH shall not be        reported.

<End of Priority Document>

The processor may include application-specific integrated circuit(ASIC), other chipset, logic circuit and/or data processing device. Thememory may include read-only memory (ROM), random access memory (RAM),flash memory, memory card, storage medium and/or other storage device.The RF unit may include baseband circuitry to process radio frequencysignals. When the embodiments are implemented in software, thetechniques described herein can be implemented with modules (e.g.,procedures, functions, and so on) that perform the functions describedherein. The modules can be stored in memory and executed by processor.The memory can be implemented within the processor or external to theprocessor in which case those can be communicatively coupled to theprocessor via various means as is known in the art.

In view of the exemplary systems described herein, methodologies thatmay be implemented in accordance with the disclosed subject matter havebeen described with reference to several flow diagrams. While forpurposed of simplicity, the methodologies are shown and described as aseries of steps or blocks, it is to be understood and appreciated thatthe claimed subject matter is not limited by the order of the steps orblocks, as some steps may occur in different orders or concurrently withother steps from what is depicted and described herein. Moreover, oneskilled in the art would understand that the steps illustrated in theflow diagram are not exclusive and other steps may be included or one ormore of the steps in the example flow diagram may be deleted withoutaffecting the scope and spirit of the present disclosure.

1. A method for changing a Discontinuous Reception (DRX) cycle in awireless communication system, performed by a wireless device, themethod comprising: configuring a short DRX cycle and a long DRX cycle;receiving a physical downlink control channel (PDCCH) indicating a newdata transmission; and using the short DRX cycle if the received PDCCHindicates the new data transmission.
 2. The method of claim 1, furthercomprising: stopping a drxShortCycleTimer if the drxShortCycleTimer isrunning.
 3. The method of claim 1, wherein the using further comprising:choosing that at least one of a Channel Quality Indicator (CQI), aPrecoding Matrix Index (PMI), a Rank Indicator (RI) and a Precoding TypeIndicator (PTI) on a Physical Uplink Control Channel (PUCCH) is reportedat an On Duration predetermined with the short DRX cycle.
 4. The methodof claim 1, wherein the receiving further comprising: checking whether anew data indicator in the PDCCH is a bit setup for a new datatransmission or not.
 5. The method of claim 1, wherein the receivingcomprising: monitoring the PDCCH at an On Duration predetermined withthe short cycle.
 6. A wireless device configured for changing aDiscontinuous Reception (DRX) cycle in a wireless communication system,comprising: a radio frequency unit configured to receive a radio signal;and a processor operatively coupled with the radio frequency unit andconfigured to: configure a short DRX cycle and a long DRX cycle; receivea physical downlink control channel (PDCCH) indicating a new datatransmission; use the short DRX cycle if the received PDCCH indicatesthe new data transmission.
 7. The wireless device of claim 6, whereinthe processor is configured to: stop a drxShortCycleTimer if thedrxShortCycleTimer is running.
 8. The wireless device of claim 6, theprocessor is configured to: choose that at least one of a ChannelQuality Indicator (CQI), a Precoding Matrix Index (PMI), a RankIndicator (RI) and a Precoding Type Indicator (PTI) on a Physical UplinkControl Channel (PUCCH) is reported at an On Duration predetermined withthe short DRX cycle.
 9. The wireless device of claim 6, the processor isconfigured to: check whether a new data indicator in the PDCCH is a bitsetup for a new data transmission or not.
 10. The wireless device ofclaim 6, the processor is configured to: monitor the PDCCH at an OnDuration predetermined with the short cycle.